Measurement method of the current-voltage characteristics of photovoltaic devices, a solar simulator for the measurement, and a module for setting irradiance and a part for adjusting irradiance used for the solar simulator

ABSTRACT

In a solar simulator for measuring the current-voltage characteristics of photovoltaic devices, it is to provide a measurement method using a solar simulator in which locative unevenness of irradiance on the test plane of the test plane side is drastically improved, not in a light source side, and a means for adjusting irradiance and the like. 
     when an object is the photovoltaic devices Ms, and the current-voltage characteristics are measured by a solar simulator Ss equipped with a light source composed of a lamp and a reflector, and a part for setting the object to be measured, in which it is possible to dispose an irradiated test plane of the object to be measured opposite an illuminating surface of said light source, the whole test plane of said photovoltaic devices is divided imaginarily into a plurality of sections and a selected member for adjusting irradiance is disposed opposite the test plane of each imaginary sections so as to equalize or substantially to equalize the irradiance by the light source at every irradiated test plane of the sections, after which light from said light source is directed onto the test plane of the object to be measured.

TECHNICAL FIELD

The present invention relates to

a measurement method in which it is possible to measure thecurrent-voltage characteristics of the photovoltaic devices by anequalized irradiance, a solar simulator for the measurement, a modulefor setting irradiance, a member for adjusting irradiance and a part foradjusting irradiance used for the measurement method by the solarsimulator.

BACKGROUND ART

There is a growing demand for the photovoltaic devices as the importancethereof has been recognized more and more as a clean energy source. Thefields where the demand for the photovoltaic devices has increased arevarious and range from power energy sources of large equipments tosmall-sized power supplies for the precision electronic devices. In thisspecification, the term “photovoltaic devices” indicates both aphotovoltaic device module (hereinafter sometimes referred to simply asa “module”) and a photovoltaic cell (hereinafter sometimes referred tosimply as a “cell”).

Wide application of the photovoltaic devices in various fields isexpected to meet various inconveniences on the part of the photovoltaicdevices user unless the characteristics or especially thecurrent-voltage characteristics of the photovoltaic devices areaccurately measured.

For that reason, a pseudo-sunlight radiator (hereinafter after referredto as a solar simulator) to measure the current-voltage characteristicsof the photovoltaic devices has conventionally been proposed and used inpractical applications. Nevertheless, there still exist problems to besolved.

Specifically, the solar simulator is used to radiate the artificiallight (pseudo-sunlight) of equalized irradiance on the test plane ofphotovoltaic devices in panel form and thus measure the current-voltagecharacteristics of the photovoltaic devices. Though the lamp is assumedto be a form considered as a spot or a line, it is very difficult toradiate the light with the equalized irradiance to the whole test plane(or whole area) of the photovoltaic devices.

In the prior art, efforts have been made to improve the problem of lightemitted with equalized irradiance mentioned above. However, most of themethods thus far developed are no more than an improvement of theoptical system or the light-emitting (lighting) circuit system of thelight source.

Improvements in the optical system or the light-emitting circuit systemof the light source of the solar simulator have been proposed in PatentDocuments 1 to 3. In spite of the improved light source, it has beendifficult to improve the locative unevenness of irradiance on the testplane of the object to be measured by less than ±2 to ±3%.

In the ordinary measurement of the photovoltaic device module, theirradiance to the effective plane section is set at 1000W/m². FIG. 1 isa diagram showing the I-V curve indicating the current-voltagecharacteristics of the object to be measured (photovoltaic devicemodule) irradiated by such irradiance comes to graphically the formillustrated in FIG. 1. In this diagram, I designates the current, and Vthe voltage.

When the locative unevenness of irradiance on the test plane is givenout by the irradiated light of the solar simulator, the I-V curvechanges as shown on FIG. 2., and therefore the current-voltagecharacteristics of the photovoltaic devices cannot be measuredcorrectly.

Incidentally, the FIG. 2 shows a comparison of the I-V curve in the fivetypes of a 96 serial module that is a photovoltaic device module with 96photovoltaic cells connected in series (herein after it is referred toas the “96 serial module”). The five types of the 96 serial module meana type of the 96 serial module having 0 cell shaded by 10% (i.e.thestate without the locative unevenness of irradiance) and four types ofthe 96 serial module having 1 cell, 2 cells, 3 cells and 10 cells,shaded by 10% respectively (i.e. the state with unevenness of irradianceof different degrees made artificially).

Curve (a) indicates the ideal state in which the locative unevenness ofirradiance on the test plane is less than ±1.0%.

Curves (b) to (e) is I-V curves of the 96 serial modules in which thelocative unevenness of irradiance of different degree is madeartificially using 1, 2, 3 and 10 object cells shaded by 10%.

As shown in the diagram of FIG. 2, when a change in the I-V curve due tothe locative unevenness of irradiance is given out, the form factorFF=Pmax/Isc×Voc (where Pmax is the maximum output of the module, Isc theshorting current, and Voc the open-circuit voltage) changes even for thephotovoltaic cells of the same configuration. This point is explainedwith reference to FIG. 3.

The FIG. 3 shows the changes of the form factor FF and the Pmax valueaccording to the quantity of cell shaded by 10% in the above mentioned96 serial module.

The left side of the ordinate is the FF (form factor in %) value and theright side of the ordinate the Pmax (maximum output, W) value.

The abscissa shows the quantity of cell shaded by 10%, used for makingthe locative unevenness of irradiance artificially.

The FF value and the Pmax value in accordance with the increase of thequantity of cell are respectively plotted and drawn by a line.

For the module in the ideal state that the locative unevenness ofirradiance is less than ±1.0% (i.e. the state that the quantity ofshaded cell is 0.), the value Pmax for is 159.1 (W) and the FF value is70.7%.

On the contrary, for each module having 1 to 4, 6, 8, 10 and 12 shadedcells used for producing artificial locative unevenness of irradiance,the Pmax value is varied from 154.2 to 152.0 (W) and the FF value isalso varied between 68.8% and 74.1%.

FIG. 4 shows the changes of the average value of the irradiance inaccordance with the varying of the quantity of cells of the 96 serialmodule in the test module as illustrated in the FIG. 3.

Curve A₁ indicates the irradiance ratio between a mean value of theirradiances measured at five points (four points at the four corners ofthe cell and one point at the center thereof) on the test plane of themodule and a mean value of the irradiances of all the cells forming thetest plane of the test module in a general measurement method.

Curve B₁ indicates the ratio between the Pmax value for zero cell shadedby 10% (no uneven irradiance) and the Pmax value of each module using 1to 12 cells shaded by 10%.

According to the Curve A₁ and the Curve B₁, it can be seen that for themodule in the ideal state (i.e. with zero shaded cell) without locativeunevenness of irradiance (less than ±1.0%), the disparity is very smallbetween the Pmax value ratio and the irradiance ratio. On the otherhand, for each test module making artificial uneven irradiance, thedisparity between the numerical values of the two curves A₁ and B₁ islarge.

The above describing shows that, it is difficult to measure the correctcurrent-voltage characteristics when there is any locative unevenness onthe test plane of the module.

[Patent Document 1] Japanese Patent Provisional Publication No. 8-235903

[Patent Document 2] Japanese Patent Provisional Publication No. 9-306201

[Patent Document 3] Japanese Patent Publication No. 6-105280

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The problem of the measurement accuracy of the current-voltagecharacteristics caused by the locative unevenness of irradiance on thetest plane cannot be radically solved simply by the improvement in theoptical system or the light-emitting circuit system of the light sourceof the solar simulator for measuring the characteristics of thephotovolatic devices.

In view of the situation, the present inventor has vigorously maderesearches and experiments, and acquired knowledge that the locativeunevenness of irradiance can be absorbed or suppressed on the test planeside of the object to be measured.

As the result of that, the present inventor has achieved the presentinvention.

Namely, the present invention is to provide a measurement method using asolar simulator for measuring the current-voltage characteristics of thephotovoltaic devices, and a means for adjusting irradiance and the likeused for the solar simulator.

In that solar simulator, the locative unevenness of irradiance on thetest plane is radically solved not on the light source unit side but onthe test plane side of an object to be measured.

Means for Solving the Problem

A first configuration for the measurement method in this inventionaiming at solving the above-mentioned problem is characterized in that,

-   when an object is the photovoltaic devices, and the current-voltage    characteristics are measured by a solar simulator equipped with a    light source composed of a lamp and a reflector, and a part for    setting the object to be measured, in which it is possible to    dispose an irradiated test plane of the object to be measured    opposite an illuminating surface of said light source, the whole    test plane of said photovoltaic devices is divided imaginarily into    a plurality of sections and a selected member for adjusting    irradiance is disposed opposite the test plane of each imaginary    sections so as to equalize or substantially to equalize the    irradiance by the light source at every irradiated test plane of the    sections, after which light from said light source is directed onto    the test plane of the object to be measured.

The member for adjusting irradiance disposed opposite the test plane ofthe respective sections is held by support means and brought close tosaid test plane, wherein the member for adjusting irradiance is formedby any one of a shading net, a shading tape and a shading sheet.

According to this invention, the support means for the member foradjusting irradiance is formed by a colorless clear resin plate withhigh photon optical transparency or a colorless clear glass plate withhigh photon optical transparency, or by a framework having alattice-like support pattern along the periphery of the respectivemembers for adjusting irradiance.

A plurality of types of units for adjusting irradiance are prepared inadvance, each part for adjusting irradiance comprising a plurality ofthe members for adjusting irradiance selected in accordance with thesize and the quantity of the test planes of the sections imaginarilyformed on a plurality of types of photovoltaic devices that are theobject to be measured, arranged in a plurality of the support means,

a required irradiance adjustment part corresponding to the object to bemeasured set in the solar simulator.

In the measurement method of the present invention described above, theoutput of the light source of the solar simulator is adjusted by using aphotovoltaic device module for setting the irradiance,

the module having the same configuration as the photovoltaic device thatis the object to be measured,

the test plane of the module divided imaginarily into a plurality ofsections,

the member for adjusting irradiance disposed on the test plane of eachof the imaginary section in order to adjust the output characteristicsof the light emitted from the light source of the solar simulator and tocorrect dispersion of the output characteristics at each imaginarysection test plane so that the irradiance at the test plane of themodule due to the illuminating light from the light source attains arequired value.

The output of the light source of the solar simulator is adjusted bysetting the required module for setting irradiance in the part forsetting the object to be measured in the solar simulator,

the modules for setting irradiance prepared in advance in accordancewith a form determined by the size and the quantity of cells of aplurality of types of photovoltaic devices of the object to be measured,

the required module for setting irradiance selected in accordance with aform of photovoltaic device to be measured from a plurality of types ofmodules for setting irradiance.

By setting the required module for setting irradiance in the part forsetting the object of the solar simulator, it is possible to raise theefficiency of the tooling change for a plurality of types ofphotovoltaic devices.

Next, the configuration of a solar simulator using for implementing themeasurement method of the present invention is characterized in that,

the light from the light source without the locative unevenness of theirradiance, i.e. equalized or substantially equalized, is irradiated tothe test plane of the photovoltaic device by using a part for adjustingirradiance set in the solar simulator equipped with a light sourcecomposed of a lamp and a reflector, and a part for setting the object inwhich it is possible to dispose an irradiated test plane of the objectto be measured opposite an illuminating surface of said light source,

a part for adjusting irradiance comprising a member for adjustingirradiance that is selected for the test plane of each of imaginarysection and disposed opposite the test plane of each of imaginarysection that the whole test plane of the photovoltaic device is dividedimaginarily into a plurality of sections,

the light from the light source irradiated to the test plane of thephotovoltaic device through the part for adjusting irradiance.

In the solar simulator mentioned above, it is desirable to use a modulefor setting irradiance in order to check whether or not the irradianceof the light source is proper and adjust the irradiance of the lightsource before a measurement. For the purpose of that, the preferredconfiguration of the module for setting irradiance is as follows;

A module for setting irradiance of a solar simulator, characterized inthat, the irradiance at the test plane of said module by the lightemitted from said light source attains a required value,

the module for setting irradiance formed by the same configuration asphotovoltaic devices of the object to be measured,

the whole test plane of said module divided imaginarily into a pluralityof sections,

the member for adjusting irradiance disposed on the test plane of eachimaginary section in order to adjust the current-voltaic characteristicsby the light emitted from the light source of a solar simulator,

the dispersion of the current-voltage characteristics in every testplane of each section corrected evenly.

The above mentioned module for setting the irradiance is composed of aplurality of the test plane of each section formed on its test plane bythe respective photovoltaic cell comprised of the module for settingirradiance as a unit or by a plurality of photovoltaic cells as a unit.

Further, in the module for setting irradiance, the current-voltagecharacteristics on the test plane of each section is equalized orsubstantially equalized by using the module for setting irradiance so asto detect the current-voltage characteristics for a respectivephotovoltaic cell as a unit composed of the test plane of each section,or for a plurality of photovoltaic cells as a unit.

Further, in the module for setting irradiance, a plurality of types ofthe module for setting irradiance are prepared in advance in accordancewith a form determined by the size and the quantity of cells of aplurality of types of photovoltaic devices of the object to be measured,and the required module for setting irradiance is selected in accordancewith the form of the photovoltaic devices of the object to be measured,and set in the part for setting the object of the solar simulator.

By setting the required module for setting irradiance in the part forsetting the object of the solar simulator, it is possible to raise theefficiency of the tooling change for a plurality of types ofphotovoltaic devices.

Next, the following is an explanation given for the configuration of apart for adjusting irradiation using to eliminate the locativeunevenness of irradiance on the test plane of the solar simulatoraccording to the present invention.

The part for adjusting the irradiance is set in the solar simulator,bringing close to the test plane of photovoltaic devices that is theobject to be measured,

the part for adjusting irradiance set at the solar simulator comprisinga member for adjusting the irradiance and making a support means holdit,

the member for adjusting the irradiance selected in accordance with theirradiance of the light from the light source to which the test plane ofeach imaginary section formed by dividing the whole plane ofphotovoltaic devices of the object to be measured imaginarily into theplural test plane sections is subjected.

The unit for adjusting irradiance is selected from a plurality of unitfor adjusting irradiance in accordance with the object to be measured inthe solar simulator and fixed at a part for setting of the part foradjusting irradiance,

the unit for adjusting irradiance comprising the member for adjustingirradiance that is selected in advance in accordance with the size andthe quantity of the test plane of each section formed respectively on aplurality of types of photovoltaic devices and disposed on a pluralityof support means.

By setting the support means to the setting part of the solar simulator,it is possible to raise the efficiency of the tooling change for aplurality of types of photovoltaic devices.

Effects of the Invention

This invention makes it possible to reduce the locative unevenness ofirradiance from the light source of a solar simulator on the test planeof photovoltaic devise of the object to be measured less than ±1.0%(though in the prior art, the locative unevenness of irradiance comes to±2 to ±3%.) by a solution as follows;

In the solar simulator used for the measurement of the current-voltagecharacteristics of photovoltaic devices equipped with a light sourcecomposed of a lamp and a reflector, and a part for setting the object tobe measured, in which it is possible to dispose the test plane of theobject to be measured opposite the illuminating surface of the lightsource, the irradiance from the light source is equalized or almostequalized every test plane of each section and

the irradiance so equalized is irradiated to the test plane of an objectto be measured,

the whole test plane of photovoltaic devices is divided imaginarily intoa plurality of test plane section and the required members for adjustingirradiance disposed on the test plane of each imaginary divided section.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings.

FIG. 5 is a plan view schematically showing an example of a photovoltaicdevice to which the invention is applicable. FIG. 6 is a longitudinalfront sectional view of FIG. 5. FIG. 7 is a sectional view schematicallyillustrating an example of a solar simulator in the present inventionfor measuring the current-voltage characteristics by the measurementmethod of the present invention. FIG. 8 is a perspective viewschematically showing an example of the members for adjusting irradiancedisposed on the prêt for adjusting irradiance set in the test plane sideof the photovoltaic device to be measured by the solar simulator shownin FIG. 7, and an example of a support means thereof. FIG. 9 is asectional view showing an example of an irradiance setting module. FIG.10 is a sectional view showing another example of the module for settingirradiance. FIG. 11 is a sectional view showing an example ofapplication of the module for setting irradiance shown in FIG. 10.

In the photovoltaic device (hereinafter referred to as the “module Ms”)providing a measuring object shown in FIGS. 5, 6, a plurality ofphotovoltaic cells Cs (hereinafter referred to as the “cells Cs”) arearranged and connected in series. In the two diagrams, a rectangularframe 1 has a test plane side 2 of a transparent plate of glass or thelike, and as shown, the cells Cs are buried in a sealing material 3 ofEVA or the like placed on the light-receiving side 2. The surface of thesealing material 3 is covered with a backing member 4 of a resin sheetor the like thereby to form an example of a module Ms. Each lead wire Rsconnecting each cell Cs is called a ribbon or a tab. Numeral 5designates an output electrode (terminal) of the module Ms.

The test plane side 2 of the module Ms is disposed opposite the lightradiation side of a light source of a conventional solar simulator. Thelight is radiated to the module Ms from the light source and thecurrent-voltage characteristics thereof are measured by detectingthrough the output terminal 5. In this measurement method, however, thelight radiated to the test plane side 2 from the light source has alocative unevenness of irradiance, and it is difficult to improve themeasurement accuracy of the current-voltage characteristics, asdescribed above.

The light source 6 shown in FIG. 7 is configured of, for example, ahousing 6 a made of a shading material and formed with an upper surfaceopened for making the light penetrate, a lamp 6 b, that is, a lightsource disposed at about the center in the housing 6 a, a reflector 6 cdisposed under the lamp 6 b, whose cross section is an arc, a reflector6 d disposed at the upper surface side of the lamp 6 b and a filter 6 efor adjusting spectrum disposed over the reflector 6 d.

The thing indicated by 6 f is a member for roughly adjusting the lightamount. However, it is selectively used if necessary. It depends on thetype of the lamp used for the light source 6 to use the filter 6 e foradjusting spectrum or not to use.

In the conventional solar simulator, a part for setting an object to bemeasured (not shown in FIG. 7) is disposed on the upper side of thelight source 6 as shown in FIG. 7, wherein the module Ms providing anobject of measurement is disposed downward on the test plane side 2faced in the part for setting the object and supported by the part forsetting the object.

The conventional solar simulator is equipped with a unit for measuringthe current-voltage characteristics and a power supply.

However, the pseudo sunlight Bs radiated from the light source unit 6,however, causes the locative unevenness of irradiance among differentareas on the test plane side 2 of the module Ms and the locativeunevenness of irradiance prevent a high-accuracy measurement of thecurrent-voltage characteristics.

According to the present invention, the locative unevenness ofirradiance is suppressed or eliminated by the part for adjustingirradiance Lc brought close to the test plane side 2 of the object. Thispoint is explained below.

In forming the part for adjusting irradiance Lc according to the presentinvention as illustrated in FIG. 8, first, the module Ms illustrated inFIGS. 5, 6 is formed with the test plane sections virtually defined foreach cell Cs. Specifically, in FIG. 5, each cell Cs forming the moduleMs as a matrix having five column sections A to E and four row sectionsi to iv constitutes an unit of the test plane section according to thepresent invention.

As for the above-mentioned module Ms having the divided test planesections, a translucent plate (not shown in the figure), having the sameform of the test plane sections as the test plane of the module Ms, isset in the part for setting the object to be measured in the solarsimulator Ss.

The translucent plate is made of a translucent material such as acrylic.

The current-voltage characteristics of each test plane section aremeasured by means that a reference cell for irradiance measurement issequentially located on each test plane section of the translucentplate.

In this way, the degree of locative unevenness of irradiance of thelight emitted from the light source 6 is detected for each area (eachtest plane section), and an area (section) with the lowest irradiance isspecified on the translucent plate.

Next, a support means 7 is formed as illustrated in FIG. 8.

The translucent member having the same specification as theaforementioned translucent plate is used for the support means.

The test plane section 8D is specified at the darkest irradiance of thesame test plane sections as the test plane of the above-mentionedtranslucent plate on the support means 7.

Based on the irradiance of the test plane section 8D, the members foradjusting irradiance are disposed on the test plane of each section inthis support means 7 to meet the irradiance of the other test planesections to the reference irradiance. However, the member for adjustingirradiance is not disposed on the test plane section 8D.

The FIG. 8 shows an example for the part for adjusting irradiance Lc inthe present invention formed by disposing three types of members foradjusting irradiance 8 (8 a to 8 c) having different shading rates tothe other test plane sections of the support means 7. In place of thetranslucent plate, a jig can be used in the form of a grid frame havingthe contour similar to each test plane section to allow the referencecell to be sequentially set.

For the convenience of explanation, FIG. 8 schematically shows a modelin which the part for adjusting irradiance Lc comprises the members foradjusting irradiance 8 a to 8 c having three different shading rates tomeet the irradiance of each test plane section to that of the darkesttest plane section 8D as the reference irradiance. Nevertheless, thequantity or size of the test plane sections or the types of the membersfor adjusting irradiance 8 as used are not limited to those of the shownmodel.

The part for adjusting irradiance Lc comprising the members foradjusting irradiance 8 a to 8 c for equaling the irradiance of the testplane sections and the supporting means 7 on which the members foradjusting irradiance 8 a to 8 c are disposed, as shown in FIG. 7, isarranged at a point about 50 to 100 mm in proximity (one example) to thetest plane side 2 of the module Ms set in the solar simulator Ss. Underthis condition, the light from the light source 6 is radiated to themodule Ms and the current-voltage characteristics of the module Ms as awhole are measured. Thus, the measurement of the current-voltagecharacteristics without the locative unevenness of irradiance on thetest plane is made possible.

The members for adjusting irradiance 8 a to 8 c used with the part foradjusting irradiance Lc may be shading nets having different meshdensities (different shading rates) coated to suppress the reflection,shading tapes formed with holes over the whole surface thereof havingdifferent shading rates or shading sheets adjustable to reduce the lighttransmission area for each test plane section. Also, the support means 7is a plastic or glass plate having a high photon optical transparency,or a grid-like frame plate formed in a hole pattern similar to thecontour of each member for adjusting irradiance 8.

The light equalized without locative unevenness of irradiance can beradiated from the light source 6 to the test plane (the test plane side2) of the object module Ms by using the part for adjusting irradiance Lcin the solar simulator Ss illustrated in FIG. 7. In this case, the lightamount on the test plane of the module Ms is so adjusted to eliminatethe locative unevenness of irradiance over the whole test plane thereofusing the members for adjusting irradiance 8 having the shadingcharacteristic, and therefore the test plane of the module Ms isrequired to be verified that the irradiance of the test plane attains areference irradiance (say, 1000 W/m²).

In the present invention, a module for setting irradiance M_(L) havingthe same configuration as the object module Ms is formed as illustratedin FIG. 9. Specifically, in the module for setting irradiance M_(L) ofthe FIG. 9, the test plane sections are formed on the test plane side 2,and the members for adjusting irradiance 8 with different shading ratesare disposed in accordance with the dispersion of the current-voltagecharacteristics of the cells on the test plane sections.

Then, whether or not the irradiance from the light source 6 accepted onall test plane of this module M_(L) satisfies the required value (say,1000 W/m²) is examined by measuring the current-voltage characteristicstaken out from an output terminal. Based on the result of thisverification, the output of the light source unit 6 is adjusted tosatisfy the required value.

The module for setting irradiance M_(L) shown in FIG. 9 comprises theselected cells Cs with the same configuration as the object module Ms,but has the dispersion of about ±2 to ±3% in the current-voltagecharacteristics. In order to suppress or eliminate the dispersion of thecurrent-voltage characteristics of the cells Cs, the members foradjusting irradiance 8 are disposed on the surface of the test planeside 2 for the respective test plane sections (the cells Cs, in thiscase).

Thereby, the irradiance to the test plane of the module for settingirradiance M_(L) is measured and examined by detecting thecurrent-voltage characteristic of the whole test plane subjected to theilluminating light of the light source from the single output terminal 5of the module M_(L).

According to the present invention, it is possible to make theirradiance on the test plane of the object module Ms set to the requiredvalue by the following steps.

As shown in FIG. 10, at first, a check terminal Tc in each of therespective cells Cs is led out of this module M_(L) from all of thecells Cs forming the module M_(L).

Next, the current-voltage characteristics in each of the respectivecells Cs is measured at each terminal Tc, and the member for adjustingirradiance 8 disposed on the test plane side 2 in each of the respectivecells Cs is selected by the result of measuring. Then, the irradiance onthe test plane of the object module Ms is set to the required value byusing the module for setting irradiance ML adjusted so that thedispersion of the current-voltaic characteristics in each of the cellsCs are eliminated.

In the module for setting irradiance M_(L) with the terminal (electrode)Tcled out of the module for each cell Cs as illustrated in FIG. 10, theterminals Tc of the cells Cs are connected in series using theconnection leads Tr as shown in FIG. 11 to form a module M_(L) havingthe same connection as the module for setting irradiance M_(L) shown inFIG. 9, and the irradiance of the whole test plane can be confirmed byusing this module M_(L).

According to the present invention, the module M_(L) is set in the partfor setting the object to be measured of the solar simulator Ss shown inFIG. 7, and after adjusting the irradiance of the light emitted from thelight source unit 6, the current-voltage characteristics of the objectmodule Ms are measured based on the light of the light source 6.

In FIG. 11, the same component elements and members as those in FIGS. 9,10 are designated by the same reference numerals, respectively.

As described above, according to the present invention, the irradianceof the test plane of the module Ms is equalized by using the part foradjusting irradiance Lc comprising the members for adjusting irradiance8 in the vicinity of the test plane 2 of the module in the part forsetting the object module Ms of the solar simulator Ss, and the light isradiated to the whole test plane from the light source 6 withoutlocative unevenness of irradiance so as to measure the current-voltagecharacteristics thereby.

Also, according to the present invention, the module for settingirradiance M_(L) is set in the part for setting the object of the solarsimulator and the irradiance of the test plane side is measured inadvance whether the irradiance of the light emitted from the lightsource 6 and radiated to the test plane side 2 of the object module Mshas the required irradiance level, and adjusted by the result of themeasuring.

The illuminating light without the locative unevenness of irradiance canbe irradiated on the object module Ms at the required predeterminedirradiance and the current versus voltage characteristics of the objectmodule Ms can be measured.

Further, according to the present invention, a plurality of types of thepart for adjusting irradiance Lc and the module for setting irradianceM_(L) are prepared as a unit in advance in accordance with the form ofthe object module Ms (size and quantity of cells of the module).

By doing that, in every time the type of the object module Ms ischanged, it is possible to select an appropriate unit from a pluralityof types of the part for adjusting irradiance Lc and the module forsetting irradiance M_(L) as unitized and adopt a plurality of types ofthe measurement aspect.

In that way, whenever the type of the object module Ms is changed, themeasurement of the current-voltage characteristics can be realizedsubstantially without any readjustment.

INDUSTRIAL APPLICABILITY

In the conventional solar simulator, in spite of the attempt to realizethe equality of irradiance by improving the optical system or thelight-emission circuit of the light source, the locative unevenness ofirradiance on the test plane could not be reduced to less than ±2% to±3%.

The present invention makes it possible to eliminate or suppress thelocative unevenness of irradiance on the test plane by dividing thewhole test plane of the photovoltaic device imaginarily into smallsections to be able to detect whether or not the irradiance attains therequired value on the test plane sections divided respectively as anunit and make it easy to adjust the irradiance if it does not attain therequired value.

Thus, the present invention has the advantages as mentioned thefollowing items of (1) to (4);

-   (1) The output characteristics of the photovoltaic device can be    measured with high accuracy.-   (2) The dispersion of the form factor FF according to the “locative    unevenness of irradiance on the test plane” can be reduced as far as    possible.-   (3) The irradiance can be adjusted directly for each intended    section (small area), and therefore the locative unevenness of    irradiance can be eliminated easily with high accuracy by    adjustment.-   (4) In accordance with the form of the photovoltaic device providing    the object of measurement, the part for adjusting irradiance and the    module for setting irradiance are prepared in advance. By doing so,    when the configuration or the form of the object module is changed,    it is possible to select the part for adjusting irradiance and the    module for setting irradiance corresponding to the configuration and    the form of each module from them and use. Thus, a high-accuracy    measurement can be realized in quick response to the change of each    object module.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] A diagram showing an example of the current-voltagecharacteristics (I-V curve) of a photovoltaic module.

[FIG. 2] A diagram showing an example of the current-voltagecharacteristics affected by locative unevenness of irradiance.

[FIG. 3] A diagram for explaining the degree that the locativeunevenness of irradiance effects to the current-voltage characteristics.

[FIG. 4] A diagram illustrating the irradiance ratio and the Pmax valueratio of the test module shown in FIG. 3.

[FIG. 5] A plan view schematically showing an example of thephotovoltaic device applied to the present invention.

[FIG. 6] A longitudinal front sectional view of FIG. 5.

[FIG. 7] A sectional view schematically illustrating an example of thesolar simulator according to the invention for measuring thecurrent-voltage characteristics by the method of the present invention.

[FIG. 8] A perspective view schematically showing an example of themembers for adjusting irradiance of the part for adjusting irradianceand the supporting means thereof set in the solar simulator of FIG. 7.

[FIG. 9] A sectional view showing an example of the module for settingirradiance.

[FIG. 10] A sectional view showing another example of the module forsetting irradiance.

[FIG. 11] A sectional view of an example of the manner in which themodule for setting irradiance shown in FIG.10 is used.

DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS

-   Ms photovoltaic module-   Cs Cell-   Rs Lead-   1 Frame-   2 the test plane side-   3 Seal member-   4 Backing member-   5 Output electrode (terminal)-   6 Light source unit-   Lc Part for adjusting irradiance-   7 Supporting means-   8 Member for adjusting irradiance-   M_(L) Module for setting irradiance

1. A measurement method of measuring a current-voltage characteristic ofan object to be measured including a plurality of photovoltaic cellsusing a solar simulator including a light source having a lamp and areflector, comprising: disposing an irradiated test plane of the objectto be measured opposite an illuminating surface of said light source;dividing a whole of the test plane of the object to be measured into aplurality of imaginary sections corresponding to respective photovoltaiccells; disposing members for adjusting irradiance opposite respectiveimaginary sections of the test plane so as to equalize or tosubstantially equalize irradiance of the object to be measured by thelight source at respective sections of the test plane corresponding tothe imaginary sections; and directing light from said light source ontothe test plane of the object to be measured, wherein the object to bemeasured produces the current-voltage characteristic to be measured inresponse to said light.
 2. A measurement method according to claim 1,further comprising: holding the members for adjusting irradiancedisposed opposite the test plane by support means; and bringing themembers for adjusting irradiance close to said test plane.
 3. Themeasurement method according to claim 2, further comprising: forming thesupport means for the members for adjusting irradiance with a colorlessclear resin plate with high photon optical transparency or a colorlessclear glass plate with high photon optical transparency, by a frameworkhaving a lattice-like support pattern along the periphery of therespective members for adjusting irradiance.
 4. The measurement methodaccording to claim 3, further comprising: adjusting an output of thelight source of the solar simulator using a photovoltaic module forsetting the irradiance, the photovoltaic module having the sameconfiguration as the photovoltaic cells of the object to be measured;dividing a test plane of the photovoltaic module into a plurality ofimaginary sections corresponding to respective photovoltaic cells; anddisposing the members for adjusting irradiance on the test plane atpositions corresponding to each imaginary section in order to correctdispersion of output characteristics of the photovoltaic cells so thatthe irradiance at the test plane of the photovoltaic cells of the objectto be measured due to the illuminating light from the light sourceattains a required value.
 5. The measurement method according to claim2, further comprising: adjusting an output of the light source of thesolar simulator using a photovoltaic module for setting the irradiance,the photovoltaic module having the same configuration as thephotovoltaic cells of the object to be measured; dividing a test planeof the photovoltaic module into a plurality of imaginary sectionscorresponding to respective photovoltaic cells; and disposing themembers for adjusting irradiance on the test plane at positionscorresponding to each imaginary section in order to correct dispersionof output characteristics of the photovoltaic cells so that theirradiance at the test plane of the photovoltaic cells of the object tobe measured due to the illuminating light from the light source attainsa required value.
 6. The measurement method according to claim 1,further comprising: forming the respective members for adjustingirradiance with any one of a shading net, a shading tape and a shadingsheet.
 7. The measurement method according to claim 6, furthercomprising: adjusting an output of the light source of the solarsimulator using a photovoltaic module for setting the irradiance, thephotovoltaic module having the same configuration as the photovoltaiccells of the object to be measured; dividing a test plane of thephotovoltaic module into a plurality of imaginary sections correspondingto respective photovoltaic cells; and disposing the members foradjusting irradiance on the test plane at positions corresponding toeach imaginary section in order to correct dispersion of outputcharacteristics of the photovoltaic cells so that the irradiance at thetest plane of the photovoltaic cells of the object to be measured due tothe illuminating light from the light source attains a required value.8. The measurement method according to claim 1, further comprising:preparing a plurality of types of parts for adjusting irradiance inadvance, the preparing of respective types of parts for adjustingirradiance comprising selecting a plurality of the members for adjustingirradiance in accordance with a size of the test plane and a quantity ofthe imaginary sections corresponding to respective photovoltaic cells;and arranging the selected members for adjusting irradiance in a supportmeans and forming into a unit.
 9. The measurement method according toclaim 8, further comprising: adjusting an output of the light source ofthe solar simulator using a photovoltaic module for setting theirradiance, the photovoltaic device module having the same configurationas the photovoltaic cells of the object to be measured; dividing a testplane of the photovoltaic module into a plurality of imaginary sectionscorresponding to respective photovoltaic cells; and disposing themembers for adjusting irradiance on the test plane at positionscorresponding to each imaginary section in order to correct dispersionof output characteristics of the photovoltaic cells so that theirradiance at the test plane of the photovoltaic cells of the object tobe measured due to the illuminating light from the light source attainsa required value.
 10. The measurement method according claim 1, furthercomprising: adjusting an output of the light source of the solarsimulator using a photovoltaic module for setting the irradiance, thephotovoltaic module having the same configuration as the photovoltaiccells of the object to be measured; dividing a test plane of thephotovoltaic module into a plurality of imaginary sections correspondingto respective photovoltaic cells; and, disposing the members foradjusting irradiance on the test plane at positions corresponding toeach imaginary section in order to correct dispersion of outputcharacteristics of the photovoltaic cells so that the irradiance at thetest plane of the photovoltaic cells of the object to be measured due tothe illuminating light from the light source attains a required value.11. The measurement method according to claim 10, further comprising:adjusting an output of the light source of the solar simulator bysetting the required module for setting irradiance in a part for settingthe object to be measured in the solar simulator; preparing the modulesfor setting irradiance in advance in accordance with a form determinedby a size and a quantity of cells of a plurality of types ofphotovoltaic devices of the object to be measured; and selecting therequired module for setting irradiance in accordance with a form ofphotovoltaic device to be measured from a plurality of types of modulesfor setting irradiance.